The human heart can suffer from various valvular diseases, which can result in significant malfunctioning of the heart and ultimately require replacement of the native heart valve with an artificial valve. There are a number of known artificial valves and a number of known methods of implanting these artificial valves in humans.
One method of implanting an artificial heart valve in a human patient is via open-chest surgery, during which the patient's heart is stopped and the patient is placed on cardiopulmonary bypass (using a so-called “heart-lung machine”). In one common surgical procedure, the diseased native valve leaflets are excised and a prosthetic valve is sutured to the surrounding tissue at the native valve annulus. Because of the trauma associated with the procedure and the attendant duration of extracorporeal blood circulation, some patients do not survive the surgical procedure or die shortly thereafter. It is well known that the risk to the patient increases with the amount of time required on extracorporeal circulation. Due to these risks, a substantial number of patients with defective native valves are deemed inoperable because their condition is too frail to withstand the procedure.
Because of the drawbacks associated with conventional open-chest surgery, percutaneous and minimally-invasive surgical approaches are in some cases preferred. In one such technique, a prosthetic valve is configured to be implanted in a much less invasive procedure by way of catheterization. For instance, U.S. Pat. Nos. 7,393,360, 7,510,575, and 7,993,394 describe collapsible transcatheter prosthetic heart valves that can be percutaneously introduced in a compressed state on a catheter and expanded to a functional size at the desired position by balloon inflation or by utilization of a self-expanding frame or stent.
Various heart valve replacement devices exist in the art and, during the past decade, advancements in valve replacement implants have been achieved. Many of these advancements have occurred with those implants delivered percutaneously in a compressed state on a catheter and, with outer sheath retraction, self-expand to a given extent for implantation. Some implants are made of entirely self-expanding structures. Other implants partially self-expand and then are further expanded by force. Such dual-expansion implants can be made from a single, substantially cylindrical, lattice structure having a pre-defined (e.g., heat-set) initial shape that is smaller than the intended implantation diameter of an anatomic orifice, such as a vessel or heart valve. The lattice can be made of nitinol, for example. A lattice of non-self-expanding material can also be used, for example, of a cobalt chromium material. Within the lattice there can be a set of adjustable expansion devices that place respective forces upon the lattice to elastically and/or plastically deform the lattice to a size that is even greater than the pre-defined shape. One example of the expansion devices is a set of jack screws that are controlled by rotating drive wires (which wires extend from the implant location to the environment outside the patient and terminate, for example, at an electronic delivery control handle). As shown in U.S. Patent Application Publication Nos. 2013/0046373, 2013/0166017, and 2014/0296962, these rotating wires are initially connected to a respective jack screw and rotation of each wire causes a corresponding rotation of the jack screw. With the jack screws being connected to the lattice on each of their opposing ends (for example, through a threaded connection on one end and a freely rotating but longitudinally fixed connection on the other), rotation in one direction expands the circumference of the lattice and rotation in the other direction contracts the lattice. These control wires can be connected to the delivery handle with temporary securement structures that keep the wires rotationally connected to the respective jack screw until implantation and release of the replacement valve is desired. Before being disconnected, the control wires can reversibly expand and contract the lattice as the surgeon desires for optimal placement in the installation location. In other words, such implants can be repositioned before final deployment. When the implant is positioned in a final desired orientation, the drive wires are disconnected from all of the jack screws and are removed from the patient.
One advantage that such implants have over entirely self-expanding lattices is that these implants can be carefully expanded and also can provide feedback to the operator as to the device diameter and forces encountered from surrounding tissue. In contrast, entirely self-expanding implants continuously expand and apply an outwardly directed force where the lattice is implanted. The final diameter of the implant is not finely controllable or adjustable. Expansion of the tissue could lead to paravalvular leakage, movement of the implant, and/or embolism, all of which are undesirable.
Another feature of lattice implants that, upon deployment, first self-expand when removed from the installation catheter and then are forcibly expanded into the delivery site (referred to as self-expanding/forcibly expanding) is the fact that the force imparted against the tissue can be measured (and/or calculated) and either minimized or set to a desired value. While rotating the drive wires, any torque applied to the drive wires can be measured and determined with an implant delivery and deployment system having sensors (e.g., electronic sensors) that measure various parameters, such as current draw for example. Rotation of the drive wires for expanding the implant can be halted when a value of the determined torque is reached.
Delivery of implants in the art for replacement or repair of a heart valve can be achieved over different avenues. One percutaneous way that implant delivery can occur is through the aorta, where the entry site in the patient is located adjacent the femoral artery, referred to as the transfemoral (TF) approach. Another route to implantation of a replacement valve is through a transapical approach. Aortic replacement valves installed in these manners are referred to as Transcatheter Aortic Valve Replacement (TAVR) and Transcatheter Aortic Valve Implantation (TAVI) surgeries, which can be transapical. A third path through the septum of the heart is also possible and one such procedure is referred as a Transseptal (TS) Antegrade Transcatheter Aortic Valve Replacement.
For the treatment of mitral valve disease, Transcatheter Mitral Valve Replacement (TMVR) has been the subject of study, but has not been widely commercialized. Current TMVR techniques have several limitations. First, the size of the valves that are available for TMVR implant may not fit well. In particular, the mitral valve is not substantially circular, it has a D-shape with a long curving interface between the mitral valve's native leaflets. This is in contrast to the aortic valve, which is substantially circular. Also, the TMVR devices do not tend to allow for repositioning of the implant once it has been deployed in place. Next, the final expanded diameter of the known TMVR devices is pre-determined, making pre-sizing by a doctor a critical and difficult step. The physician must remotely assess the size of the diseased valve for selecting the correct implant. Migration of existing mitral valve implants is a significant clinical problem, potentially causing leakage and/or compromising necessary vascular supply. In such situations, emergency open surgery can be required, and/or it can lead to an unstable seal and/or migration.
No commercially approved transcatheter mitral valve exists. Some are being studied but there is no replacement mitral valve that can be fully repositioned during deployment and adjusted to better accommodate and seal a natural, diseased mitral valve. Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.